Early Cretaceous (Neocomian-Cenomanian) Palynomorphs

INTRODUCTION This study is primarily concerned with the Neocomian to Aptian palynomorphs recorded in selected exploration wells (See Fig. 9). In order to document a complete Early Cretaceous microfloral succession in the studied wells, a reconnaissance of Aptian to Early Cenomanian palynomorphs was also undertaken. Details of the results from this younger interval appear in a later section. Palynomorph assemblages vary in preservation and character. To the north, sandstone, siltstone and shale deposited in shallow-marine environments, contain well-preserved assemblages of dinoflagellate cysts, pollen and spores which can be used for stage-level age determination. A majority of the samples analysed, however, contain moderate numbers of dinoflagellate cysts, but fewer miospores. The abundance of land derived detritus indicates the relatively close proximity of the shoreline. In the central and southern parts of the study area, sandstone and siltstone that are deposited in non-marine, fluvial, lacustrine or lagoonal environments show a general paucity of well-preserved palynofloras. Miospores of stratigraphic value are generally rare or absent although the majority of the samples are dominated by land derived detritus. PALYNOMORPH SUCCESSION The majority of the wells from northern Cyrenaica show a hiatus at the Jurassic Cretaceous boundary. Late Neocomian or Aptian sediments occur immediately above Middle or early Late Jurassic sediments. Well preserved Neocomian palynomorphs were recorded in wells A1-36, B1-36, Bla-18 and A1-45. The stratigraphical ranges of palynomorphs presented on the plate explanations are local ranges and are based on the studied intervals only. A preliminary palynological zonation of Late Jurassic (Late Kimmeridgian) to . . .


INTRODUCTION
This study is primarily concerned with the Neocomian to Aptian palynomorphs recorded in selected exploration wells (See Fig. 9). In order to document a complete Early Cretaceous microfloral succession in the studied wells, a reconnaissance of Aptian to Early Cenomanian palynomorphs was also undertaken. Details of the results from this younger interval appear in a later section.
Palynomorph assemblages vary in preservation and character. To the north, sandstone, siltstone and shale deposited in shallow-marine environments, contain wellpreserved assemblages of dinoflagellate cysts, pollen and spores which can be used for stage-level age determination. A majority of the samples analysed, however, contain moderate numbers of dinoflagellate cysts, but fewer miospores. The abundance of land derived detritus indicates the relatively close proximity of the shoreline. In the central and southern parts of the study area, sandstone and siltstone that are deposited in nonmarine, fluvial, lacustrine or lagoonal environments show a general paucity of well-preserved palynofloras. Miospores of stratigraphic value are generally rare or absent although the majority of the samples are dominated by land derived detritus.

PALYNOMORPH SUCCESSION
The majority of the wells from northern Cyrenaica show a hiatus at the Jurassic Cretaceous boundary. Late Neocomian or Aptian sediments occur immediately above Middle or early Late Jurassic sediments. Well preserved Neocomian palynomorphs were recorded in wells A1-36, B1-36, Bla-18 and A1-45. The stratigraphical ranges of palynomorphs presented on the plate explanations are local ranges and are based on the studied intervals only. A preliminary palynological zonation of Late Jurassic (Late Kimmeridgian) to Late Cretaceous (Cenomanian) is presented in Fig. 9. This zonation is based on samples dated independently on microfaunal assemblages. Further refinement of this zonation is currently in progress.
Aptian dinoflagellate cyst assemblages contain abundant representatives of Subtilisphaera senegalensis and Subtilisphaera sp. together with rare Pseudoceratium regium and Cribroperidinium edwardsii. Miospores from this interval contain the firs$ appearance of Afropollis spp., Reyrea polymorpha, Retitricolpites spp., Psilatricolpites spp. and Eucomiidites sp. Classopollis is represented by abundant species of less than 30 microns. A number of species which disappear during this interval include "Inaperturopollenites" crisopolensis, Stellatopollis cf. barghoornii, Callialasporites spp., and Appendicisporites spp. Ephedripites spp., present in the Neocomian is more frequently encountered during the late Early Cretaceous. Inaperturate pollen, Crybelosp o rites, Cicatricosispo rites, Con ca visporites and Pilosisporites continue as infrequent members of the assemblages.
Albian-Cenomanian palynomorph assemblages contain a number of distinctive dinoflagellate cysts including Xenascus ceratioides, Cyclonephelium vanno-phorum and Florentina spp. Miospore assemblages from this interval are distinguished by the earliest appearance during the Albian of Elaterosporites klaszii and Elaterocolpites castelainii together with Sofrepites legouxae, tricolporate and triporate angiosperm pollen. Species of Classopollis less than 30 microns are replaced by larger forms of which C . brasiliensis is a good stratigraphic marker. Species of Afropollis and of the Elaterosporites group disappear in the Early Cenomanian but Cicatricosisporites, Crybelosporites, Retimonocolpites, Tricolpites and inaperturate pollen continue to occur.

SARIR (NUBIAN) SANDSTONE
Sediments from within this unit, in the central and southern parts of the project area, where it was deposited in fluvial, lacustrine or lagoonal environments show a general paucity of well preserved palynomorphs. Miospores of stratigraphical value are generally rare. Taxa frequently present include Cerebropollenites mesozoicus, Concavisporites spp., Classopollis spp., Araucariacites sp. and rarely Alisporites sp. These miospores are not age diagnostic but suggest a Late Jurassic-Early Cretaceous age for the Sarir or Nubian sandstone. Samples from a limited number of wells have yielded microfloras which can be dated confidently as Neocomian-             (Neocomian-Cenomanian).

Explanation of Plate 60
All figures are X 500